<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="css/style.css">
</head>
<body>
    <div id="nav">
        <h2 class="title">全部商品分类</h2>
        <ul>
            <li><a href="#">a1</a>&nbsp;<a href="#">a2</a>&nbsp;<a href="#">a3</a></li>
            <li><a href="#">b1</a>&nbsp;<a href="#">b2</a>&nbsp;<a href="#">b3</a></li>
            <li><a href="#">c1</a>&nbsp;<a href="#">c2</a>&nbsp;<a href="#">c3</a></li>
            <li><a href="#">d1</a>&nbsp;<a href="#">d2</a>&nbsp;<a href="#">d3</a></li>
        </ul>
    </div>

</body>
</html>